Added ability to save tensors

README.md

@@ -36,6 +36,7 @@ Quick Usage
 ```python
 import torchaudio
 sound, sample_rate = torchaudio.load('foo.mp3')
+torchaudio.save('foo_save.mp3', sound, sample_rate) # saves tensor to file
 ```
 
 API Reference
@@ -49,3 +50,13 @@ audio.load(
 )
 ```
 
+torchaudio.save
+```
+saves a tensor into an audio file. The extension of the given path is used as the saving format.
+audio.save(
+	string, # path to file
+	tensor, # NSamples x NChannels 2D tensor
+	number, # sample_rate of the audio to be saved as
+)
+```
+

torchaudio/__init__.py

@@ -1,32 +1,40 @@
+import os
+
 import torch
 
 from cffi import FFI
+
 ffi = FFI()
 from ._ext import th_sox
 
+
+def check_input(src):
+    if not torch.is_tensor(src):
+        raise TypeError('Expected a tensor, got %s' % type(src))
+    if not src.__module__ == 'torch':
+        raise TypeError('Expected a CPU based tensor, got %s' % type(src))
+
+
 def load(filename, out=None):
     if out is not None:
-        assert torch.is_tensor(out)
-        assert not out.is_cuda
+        check_input(out)
     else:
         out = torch.FloatTensor()
-
-    if isinstance(out, torch.FloatTensor):
-        func = th_sox.libthsox_Float_read_audio_file
-    elif isinstance(out, torch.DoubleTensor):
-        func = th_sox.libthsox_Double_read_audio_file
-    elif isinstance(out, torch.ByteTensor):
-        func = th_sox.libthsox_Byte_read_audio_file
-    elif isinstance(out, torch.CharTensor):
-        func = th_sox.libthsox_Char_read_audio_file
-    elif isinstance(out, torch.ShortTensor):
-        func = th_sox.libthsox_Short_read_audio_file
-    elif isinstance(out, torch.IntTensor):
-        func = th_sox.libthsox_Int_read_audio_file
-    elif isinstance(out, torch.LongTensor):
-        func = th_sox.libthsox_Long_read_audio_file
-
-    sample_rate_p = ffi.new('int*')    
+    typename = type(out).__name__.replace('Tensor', '')
+    func = getattr(th_sox, 'libthsox_{}_read_audio_file'.format(typename))
+    sample_rate_p = ffi.new('int*')
     func(bytes(filename), out, sample_rate_p)
     sample_rate = sample_rate_p[0]
     return out, sample_rate
+
+
+def save(filepath, src, sample_rate):
+    filename, extension = os.path.splitext(filepath)
+    if type(sample_rate) != int:
+        raise TypeError('Sample rate should be a integer')
+
+    check_input(src)
+    typename = type(src).__name__.replace('Tensor', '')
+    func = getattr(th_sox, 'libthsox_{}_write_audio_file'.format(typename))
+
+    func(bytes(filepath), src, extension[1:], sample_rate)

torchaudio/src/generic/th_sox.c

@@ -44,4 +44,55 @@ void libthsox_(read_audio_file)(const char *file_name, THTensor* tensor, int* sa
   sox_close(fd);
 }
 
+void libthsox_(write_audio)(sox_format_t *fd, THTensor* src,
+			  const char *extension, int sample_rate)
+{
+  long nchannels = src->size[1];
+  long nsamples = src->size[0];
+  real* data = THTensor_(data)(src);
+
+  // convert audio to dest tensor
+  int x,k;
+  for (x=0; x<nsamples; x++) {
+    for (k=0; k<nchannels; k++) {
+      int32_t sample = (int32_t)(data[x*nchannels+k]);
+      size_t samples_written = sox_write(fd, &sample, 1);
+      if (samples_written != 1)
+	THError("[write_audio_file] write failed in sox_write");
+    }
+  }
+}
+
+void libthsox_(write_audio_file)(const char *file_name, THTensor* src,
+			       const char *extension, int sample_rate)
+{
+  if (THTensor_(isContiguous)(src) == 0)
+    THError("[write_audio_file] Input should be contiguous tensors");
+
+  long nchannels = src->size[1];
+  long nsamples = src->size[0];
+
+  sox_format_t *fd;
+
+  // Create sox objects and write into int32_t buffer
+  sox_signalinfo_t sinfo;
+  sinfo.rate = sample_rate;
+  sinfo.channels = nchannels;
+  sinfo.length = nsamples * nchannels;
+  sinfo.precision = sizeof(int32_t) * 8; /* precision in bits */
+#if SOX_LIB_VERSION_CODE >= 918272 // >= 14.3.0
+  sinfo.mult = NULL;
+#endif
+  fd = sox_open_write(file_name, &sinfo, NULL, extension, NULL, NULL);
+  if (fd == NULL)
+    THError("[write_audio_file] Failure to open file for writing");
+
+  libthsox_(write_audio)(fd, src, extension, sample_rate);
+
+  // free buffer and sox structures
+  sox_close(fd);
+
+  return;
+}
+
 #endif

torchaudio/src/generic/th_sox.h

@@ -3,4 +3,5 @@
 #else
 
 void libthsox_(read_audio_file)(const char *file_name, THTensor* tensor, int* sample_rate);
+void libthsox_(write_audio_file)(const char *file_name, THTensor* src, const char *extension, int sample_rate);
 #endif

torchaudio/src/th_sox.h

@@ -15,3 +15,18 @@ void libthsox_Char_read_audio_file(const char *file_name, THCharTensor* tensor,
 void libthsox_Short_read_audio_file(const char *file_name, THShortTensor* tensor, int* sample_rate);
 void libthsox_Int_read_audio_file(const char *file_name, THIntTensor* tensor, int* sample_rate);
 void libthsox_Long_read_audio_file(const char *file_name, THLongTensor* tensor, int* sample_rate);
+
+void libthsox_Float_write_audio_file(const char *file_name, THFloatTensor* tensor, const char *extension,
+                                        int sample_rate);
+void libthsox_Double_write_audio_file(const char *file_name, THDoubleTensor* tensor, const char *extension,
+                                        int sample_rate);
+void libthsox_Byte_write_audio_file(const char *file_name, THByteTensor* tensor, const char *extension,
+                                        int sample_rate);
+void libthsox_Char_write_audio_file(const char *file_name, THCharTensor* tensor, const char *extension,
+                                        int sample_rate);
+void libthsox_Short_write_audio_file(const char *file_name, THShortTensor* tensor, const char *extension,
+                                        int sample_rate);
+void libthsox_Int_write_audio_file(const char *file_name, THIntTensor* tensor, const char *extension,
+                                        int sample_rate);
+void libthsox_Long_write_audio_file(const char *file_name, THLongTensor* tensor, const char *extension,
+                                        int sample_rate);